An electronic flash device that radiates artificial light onto a subject being photographed may illuminate the subject by altering the color temperature of the illuminating light for optimal photographic expression. In addition, in an environment in which the color temperature of light illuminating the subject changes, e.g., an environment in which the illuminating light switches from sunlight to incandescent light, the color temperature may be corrected by inserting a color glass filter in an optical system of the camera so as to accurately reproduce the color tone. However, only limited color temperature correction is achieved and the color temperature cannot be corrected in a continuous manner either by combining the use of auxiliary light from a strobe or by using a color glass filter.
An imaging filter constituted with a liquid crystal is used in the known art in order to continuously correct the color temperature over a wide range (for instance, patent reference literature 1). Through such a color temperature correction filter, which is formed by filling a cell with a guest host liquid crystal material containing a dichroic pigment varying light absorption characteristics in correspondence to specific molecular arrangements, the color temperature of the incident light is altered by controlling the arrangement of the pigment molecules and thus altering the level of the absorption of light with a short wavelength as a voltage is applied to the liquid crystal.
Patent reference literature 1: Japanese Laid Open Patent Publication No. 2001-054121 (page 3 and FIGS. 1 and 3)